1. Field of the Invention
The present invention relates to an endoscope apparatus, and particularly to an endoscope apparatus which includes a focusing mechanism.
2. Description of the Related Art
In an endoscope which includes an imaging unit at a front end section, and a flexible tube having a bent portion, normally, for observing an endoscope image in an optimum condition, it is necessary to perform focusing by moving a focusing lens and an imaging device. For this, an imaging apparatus for endoscope has been proposed in Japanese Patent Application Laid-open Publication No. 2004-129950. In the imaging apparatus for endoscope according to the Japanese Patent Application Laid-open Publication No. 2004-129950, inside a front end section of the endoscope, a shape memory alloy is used as a means for varying relative positions of an optical device and an imaging device.
In an endoscope apparatus disclosed in Japanese Patent Application Laid-open Publication No. 2004-129950, inside the front end section of the endoscope which is rigid, the relative positions of the optical device and the imaging device are changed by using the shape memory alloy. The endoscope is structured such that focusing is performed by changing the relative positions of the optical device and the imaging device.
However, an amount of change in the relative positions of the optical device and the imaging device is attributable to a length of the shape memory alloy which is included in the front end section of the endoscope, which is rigid. Since the rigid front end section of the endoscope cannot be made substantially long, from a point of view of functions of the endoscope, a length of the shape memory alloy inside the front end section of the endoscope is restricted. Therefore, in a structure according to a conventional technology, an increase in the amount of change in the relative positions of the optical device and the imaging device for focusing cannot be dealt with.